Charging a vehicle battery pack in a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a battery electric vehicle (BEV), or some other type of vehicle can sometimes result in an overcharged or undercharged battery condition; neither of which is particularly desirable.
An overcharged battery condition may result in a breakdown of the electrolytic material, gassing, swelling, overheating and/or other undesirable phenomena that can diminish the overall performance or state of the battery pack. Overcharging can occur, for example, when a battery pack is left charging at a relatively low current for a significant amount of time. An undercharged battery pack, on the other hand, may be a performance handicap because energy that is otherwise available for the battery pack is left unutilized. For instance, certain vehicle battery packs have a voltage threshold or voltage lid that exceeds the 100% state-of-charge (SOC) voltage for the battery pack (this may allow for rapid charging during regenerative braking and other events that involve high amounts of current for short periods of time). If the voltage threshold for a battery pack is set too low, then energy that is otherwise available for the battery pack is left unused.
Therefore, there may be a need for a method that determines a voltage threshold for a vehicle battery pack and takes overcharged and undercharged considerations into account.